/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory.support;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.TypeConverter;
import org.springframework.beans.factory.*;
import org.springframework.beans.factory.config.*;
import org.springframework.core.OrderComparator;
import org.springframework.core.ResolvableType;
import org.springframework.core.annotation.MergedAnnotation;
import org.springframework.core.annotation.MergedAnnotations;
import org.springframework.core.annotation.MergedAnnotations.SearchStrategy;
import org.springframework.core.log.LogMessage;
import org.springframework.lang.Nullable;
import org.springframework.util.*;

import javax.inject.Provider;
import java.io.*;
import java.lang.annotation.Annotation;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.stream.Stream;

/**
 * Spring's default implementation of the {@link ConfigurableListableBeanFactory}
 * and {@link BeanDefinitionRegistry} interfaces: a full-fledged bean factory
 * based on bean definition metadata, extensible through post-processors.
 *
 * <p>Typical usage is registering all bean definitions first (possibly read
 * from a bean definition file), before accessing beans. Bean lookup by name
 * is therefore an inexpensive operation in a local bean definition table,
 * operating on pre-resolved bean definition metadata objects.
 *
 * <p>Note that readers for specific bean definition formats are typically
 * implemented separately rather than as bean factory subclasses:
 * see for example {@link PropertiesBeanDefinitionReader} and
 * {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader}.
 *
 * <p>For an alternative implementation of the
 * {@link org.springframework.beans.factory.ListableBeanFactory} interface,
 * have a look at {@link StaticListableBeanFactory}, which manages existing
 * bean instances rather than creating new ones based on bean definitions.
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @author Costin Leau
 * @author Chris Beams
 * @author Phillip Webb
 * @author Stephane Nicoll
 * @see #registerBeanDefinition
 * @see #addBeanPostProcessor
 * @see #getBean
 * @see #resolveDependency
 * @since 16 April 2001
 */
@SuppressWarnings("serial")
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {

    @Nullable
    private static Class<?> javaxInjectProviderClass;

    static {
        try{
            javaxInjectProviderClass = ClassUtils.forName("javax.inject.Provider",
                    DefaultListableBeanFactory.class.getClassLoader());
        }catch(ClassNotFoundException ex){
            // JSR-330 API not available - Provider interface simply not supported then.
            javaxInjectProviderClass = null;
        }
    }

    /** Map from serialized id to factory instance. */
    private static final Map<String, Reference<DefaultListableBeanFactory>> serializableFactories =
            new ConcurrentHashMap<>(8);

    /** Optional id for this factory, for serialization purposes. */
    @Nullable
    private String serializationId;

    /** Whether to allow re-registration of a different definition with the same name. */
    private boolean allowBeanDefinitionOverriding = true;

    /** Whether to allow eager class loading even for lazy-init beans. */
    private boolean allowEagerClassLoading = true;

    /** Optional OrderComparator for dependency Lists and arrays. */
    @Nullable
    private Comparator<Object> dependencyComparator;

    /** Resolver to use for checking if a bean definition is an autowire candidate. */
    private AutowireCandidateResolver autowireCandidateResolver = new SimpleAutowireCandidateResolver();

    /** Map from dependency type to corresponding autowired value. */
    private final Map<Class<?>, Object> resolvableDependencies = new ConcurrentHashMap<>(16);

    /** Map of bean definition objects, keyed by bean name. */
    private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);

    /** Map of singleton and non-singleton bean names, keyed by dependency type. */
    private final Map<Class<?>, String[]> allBeanNamesByType = new ConcurrentHashMap<>(64);

    /** Map of singleton-only bean names, keyed by dependency type. */
    private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<>(64);

    /** List of bean definition names, in registration order. */
    private volatile List<String> beanDefinitionNames = new ArrayList<>(256);

    /** List of names of manually registered singletons, in registration order. */
    private volatile Set<String> manualSingletonNames = new LinkedHashSet<>(16);

    /** Cached array of bean definition names in case of frozen configuration. */
    @Nullable
    private volatile String[] frozenBeanDefinitionNames;

    /** Whether bean definition metadata may be cached for all beans. */
    private volatile boolean configurationFrozen = false;

    /**
     * Create a new DefaultListableBeanFactory.
     */
    public DefaultListableBeanFactory() {
        super();
    }

    /**
     * Create a new DefaultListableBeanFactory with the given parent.
     * @param parentBeanFactory the parent BeanFactory
     */
    public DefaultListableBeanFactory(@Nullable BeanFactory parentBeanFactory) {
        super(parentBeanFactory);
    }

    /**
     * Specify an id for serialization purposes, allowing this BeanFactory to be
     * deserialized from this id back into the BeanFactory object, if needed.
     */
    public void setSerializationId(@Nullable String serializationId) {
        if(serializationId != null){
            serializableFactories.put(serializationId, new WeakReference<>(this));
        }else if(this.serializationId != null){
            serializableFactories.remove(this.serializationId);
        }
        this.serializationId = serializationId;
    }

    /**
     * Return an id for serialization purposes, if specified, allowing this BeanFactory
     * to be deserialized from this id back into the BeanFactory object, if needed.
     * @since 4.1.2
     */
    @Nullable
    public String getSerializationId() {
        return this.serializationId;
    }

    /**
     * Set whether it should be allowed to override bean definitions by registering
     * a different definition with the same name, automatically replacing the former.
     * If not, an exception will be thrown. This also applies to overriding aliases.
     * <p>Default is "true".
     * @see #registerBeanDefinition
     */
    public void setAllowBeanDefinitionOverriding(boolean allowBeanDefinitionOverriding) {
        this.allowBeanDefinitionOverriding = allowBeanDefinitionOverriding;
    }

    /**
     * Return whether it should be allowed to override bean definitions by registering
     * a different definition with the same name, automatically replacing the former.
     * @since 4.1.2
     */
    public boolean isAllowBeanDefinitionOverriding() {
        return this.allowBeanDefinitionOverriding;
    }

    /**
     * Set whether the factory is allowed to eagerly load bean classes
     * even for bean definitions that are marked as "lazy-init".
     * <p>Default is "true". Turn this flag off to suppress class loading
     * for lazy-init beans unless such a bean is explicitly requested.
     * In particular, by-type lookups will then simply ignore bean definitions
     * without resolved class name, instead of loading the bean classes on
     * demand just to perform a type check.
     * @see AbstractBeanDefinition#setLazyInit
     */
    public void setAllowEagerClassLoading(boolean allowEagerClassLoading) {
        this.allowEagerClassLoading = allowEagerClassLoading;
    }

    /**
     * Return whether the factory is allowed to eagerly load bean classes
     * even for bean definitions that are marked as "lazy-init".
     * @since 4.1.2
     */
    public boolean isAllowEagerClassLoading() {
        return this.allowEagerClassLoading;
    }

    /**
     * Set a {@link java.util.Comparator} for dependency Lists and arrays.
     * @see org.springframework.core.OrderComparator
     * @see org.springframework.core.annotation.AnnotationAwareOrderComparator
     * @since 4.0
     */
    public void setDependencyComparator(@Nullable Comparator<Object> dependencyComparator) {
        this.dependencyComparator = dependencyComparator;
    }

    /**
     * Return the dependency comparator for this BeanFactory (may be {@code null}.
     * @since 4.0
     */
    @Nullable
    public Comparator<Object> getDependencyComparator() {
        return this.dependencyComparator;
    }

    /**
     * Set a custom autowire candidate resolver for this BeanFactory to use
     * when deciding whether a bean definition should be considered as a
     * candidate for autowiring.
     */
    public void setAutowireCandidateResolver(final AutowireCandidateResolver autowireCandidateResolver) {
        Assert.notNull(autowireCandidateResolver, "AutowireCandidateResolver must not be null");
        if(autowireCandidateResolver instanceof BeanFactoryAware){
            if(System.getSecurityManager() != null){
                AccessController.doPrivileged((PrivilegedAction<Object>)() -> {
                    ((BeanFactoryAware)autowireCandidateResolver).setBeanFactory(DefaultListableBeanFactory.this);
                    return null;
                }, getAccessControlContext());
            }else{
                ((BeanFactoryAware)autowireCandidateResolver).setBeanFactory(this);
            }
        }
        this.autowireCandidateResolver = autowireCandidateResolver;
    }

    /**
     * Return the autowire candidate resolver for this BeanFactory (never {@code null}).
     */
    public AutowireCandidateResolver getAutowireCandidateResolver() {
        return this.autowireCandidateResolver;
    }

    @Override
    public void copyConfigurationFrom(ConfigurableBeanFactory otherFactory) {
        super.copyConfigurationFrom(otherFactory);
        if(otherFactory instanceof DefaultListableBeanFactory){
            DefaultListableBeanFactory otherListableFactory = (DefaultListableBeanFactory)otherFactory;
            this.allowBeanDefinitionOverriding = otherListableFactory.allowBeanDefinitionOverriding;
            this.allowEagerClassLoading = otherListableFactory.allowEagerClassLoading;
            this.dependencyComparator = otherListableFactory.dependencyComparator;
            // A clone of the AutowireCandidateResolver since it is potentially BeanFactoryAware...
            setAutowireCandidateResolver(BeanUtils.instantiateClass(otherListableFactory.getAutowireCandidateResolver()
                                                                                        .getClass()));
            // Make resolvable dependencies (e.g. ResourceLoader) available here as well...
            this.resolvableDependencies.putAll(otherListableFactory.resolvableDependencies);
        }
    }

    //---------------------------------------------------------------------
    // Implementation of remaining BeanFactory methods
    //---------------------------------------------------------------------

    @Override
    public <T> T getBean(Class<T> requiredType) throws BeansException {
        return getBean(requiredType, (Object[])null);
    }

    @SuppressWarnings("unchecked")
    @Override
    public <T> T getBean(Class<T> requiredType, @Nullable Object... args) throws BeansException {
        Assert.notNull(requiredType, "Required type must not be null");
        Object resolved = resolveBean(ResolvableType.forRawClass(requiredType), args, false);
        if(resolved == null){
            throw new NoSuchBeanDefinitionException(requiredType);
        }
        return (T)resolved;
    }

    @Override
    public <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType) throws BeansException {
        Assert.notNull(requiredType, "Required type must not be null");
        return getBeanProvider(ResolvableType.forRawClass(requiredType));
    }

    @SuppressWarnings("unchecked")
    @Override
    public <T> ObjectProvider<T> getBeanProvider(ResolvableType requiredType) {
        return new BeanObjectProvider<T>() {
            @Override
            public T getObject() throws BeansException {
                T resolved = resolveBean(requiredType, null, false);
                if(resolved == null){
                    throw new NoSuchBeanDefinitionException(requiredType);
                }
                return resolved;
            }

            @Override
            public T getObject(Object... args) throws BeansException {
                T resolved = resolveBean(requiredType, args, false);
                if(resolved == null){
                    throw new NoSuchBeanDefinitionException(requiredType);
                }
                return resolved;
            }

            @Override
            @Nullable
            public T getIfAvailable() throws BeansException {
                return resolveBean(requiredType, null, false);
            }

            @Override
            @Nullable
            public T getIfUnique() throws BeansException {
                return resolveBean(requiredType, null, true);
            }

            @Override
            public Stream<T> stream() {
                return Arrays.stream(getBeanNamesForTypedStream(requiredType))
                             .map(name -> (T)getBean(name))
                             .filter(bean -> !(bean instanceof NullBean));
            }

            @Override
            public Stream<T> orderedStream() {
                String[] beanNames = getBeanNamesForTypedStream(requiredType);
                Map<String, T> matchingBeans = new LinkedHashMap<>(beanNames.length);
                for(String beanName: beanNames){
                    Object beanInstance = getBean(beanName);
                    if(!(beanInstance instanceof NullBean)){
                        matchingBeans.put(beanName, (T)beanInstance);
                    }
                }
                Stream<T> stream = matchingBeans.values().stream();
                return stream.sorted(adaptOrderComparator(matchingBeans));
            }
        };
    }

    @Nullable
    private <T> T resolveBean(ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) {
        NamedBeanHolder<T> namedBean = resolveNamedBean(requiredType, args, nonUniqueAsNull);
        if(namedBean != null){
            return namedBean.getBeanInstance();
        }
        BeanFactory parent = getParentBeanFactory();
        if(parent instanceof DefaultListableBeanFactory){
            return ((DefaultListableBeanFactory)parent).resolveBean(requiredType, args, nonUniqueAsNull);
        }else if(parent != null){
            ObjectProvider<T> parentProvider = parent.getBeanProvider(requiredType);
            if(args != null){
                return parentProvider.getObject(args);
            }else{
                return (nonUniqueAsNull?parentProvider.getIfUnique():parentProvider.getIfAvailable());
            }
        }
        return null;
    }

    private String[] getBeanNamesForTypedStream(ResolvableType requiredType) {
        return BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this, requiredType);
    }

    //---------------------------------------------------------------------
    // Implementation of ListableBeanFactory interface
    //---------------------------------------------------------------------

    @Override
    public boolean containsBeanDefinition(String beanName) {
        Assert.notNull(beanName, "Bean name must not be null");
        return this.beanDefinitionMap.containsKey(beanName);
    }

    @Override
    public int getBeanDefinitionCount() {
        return this.beanDefinitionMap.size();
    }

    @Override
    public String[] getBeanDefinitionNames() {
        String[] frozenNames = this.frozenBeanDefinitionNames;
        if(frozenNames != null){
            return frozenNames.clone();
        }else{
            return StringUtils.toStringArray(this.beanDefinitionNames);
        }
    }

    @Override
    public String[] getBeanNamesForType(ResolvableType type) {
        return getBeanNamesForType(type, true, true);
    }

    @Override
    public String[] getBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
        Class<?> resolved = type.resolve();
        if(resolved != null && !type.hasGenerics()){
            return getBeanNamesForType(resolved, includeNonSingletons, includeNonSingletons);
        }else{
            return doGetBeanNamesForType(type, includeNonSingletons, includeNonSingletons);
        }
    }

    @Override
    public String[] getBeanNamesForType(@Nullable Class<?> type) {
        return getBeanNamesForType(type, true, true);
    }

    @Override
    public String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
        if(!isConfigurationFrozen() || type == null || !allowEagerInit){
            return doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, allowEagerInit);
        }
        Map<Class<?>, String[]> cache = (includeNonSingletons?this.allBeanNamesByType:this.singletonBeanNamesByType);
        String[] resolvedBeanNames = cache.get(type);
        if(resolvedBeanNames != null){
            return resolvedBeanNames;
        }
        resolvedBeanNames = doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, true);
        if(ClassUtils.isCacheSafe(type, getBeanClassLoader())){
            cache.put(type, resolvedBeanNames);
        }
        return resolvedBeanNames;
    }

    private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
        List<String> result = new ArrayList<>();

        // Check all bean definitions.
        for(String beanName: this.beanDefinitionNames){
            // Only consider bean as eligible if the bean name
            // is not defined as alias for some other bean.
            if(!isAlias(beanName)){
                try{
                    RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                    // Only check bean definition if it is complete.
                    if(!mbd.isAbstract() && (allowEagerInit
                            || (mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading())
                            && !requiresEagerInitForType(mbd.getFactoryBeanName()))){
                        boolean isFactoryBean = isFactoryBean(beanName, mbd);
                        BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
                        boolean matchFound = false;
                        boolean allowFactoryBeanInit = allowEagerInit || containsSingleton(beanName);
                        boolean isNonLazyDecorated = dbd != null && !mbd.isLazyInit();
                        if(!isFactoryBean){
                            if(includeNonSingletons || isSingleton(beanName, mbd, dbd)){
                                matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
                            }
                        }else{
                            if(includeNonSingletons || isNonLazyDecorated || (allowFactoryBeanInit
                                    && isSingleton(beanName, mbd, dbd))){
                                matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
                            }
                            if(!matchFound){
                                // In case of FactoryBean, try to match FactoryBean instance itself next.
                                beanName = FACTORY_BEAN_PREFIX + beanName;
                                matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
                            }
                        }
                        if(matchFound){
                            result.add(beanName);
                        }
                    }
                }catch(CannotLoadBeanClassException | BeanDefinitionStoreException ex){
                    if(allowEagerInit){
                        throw ex;
                    }
                    // Probably a placeholder: let's ignore it for type matching purposes.
                    LogMessage message = (ex instanceof CannotLoadBeanClassException)?LogMessage.format("Ignoring "
                            + "bean class loading failure for bean '%s'", beanName):LogMessage
                            .format("Ignoring unresolvable metadata in bean definition '%s'", beanName);
                    logger.trace(message, ex);
                    onSuppressedException(ex);
                }
            }
        }

        // Check manually registered singletons too.
        for(String beanName: this.manualSingletonNames){
            try{
                // In case of FactoryBean, match object created by FactoryBean.
                if(isFactoryBean(beanName)){
                    if((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)){
                        result.add(beanName);
                        // Match found for this bean: do not match FactoryBean itself anymore.
                        continue;
                    }
                    // In case of FactoryBean, try to match FactoryBean itself next.
                    beanName = FACTORY_BEAN_PREFIX + beanName;
                }
                // Match raw bean instance (might be raw FactoryBean).
                if(isTypeMatch(beanName, type)){
                    result.add(beanName);
                }
            }catch(NoSuchBeanDefinitionException ex){
                // Shouldn't happen - probably a result of circular reference resolution...
                logger.trace(LogMessage.format("Failed to check manually registered singleton with name '%s'",
                        beanName), ex);
            }
        }

        return StringUtils.toStringArray(result);
    }

    private boolean isSingleton(String beanName, RootBeanDefinition mbd, @Nullable BeanDefinitionHolder dbd) {
        return (dbd != null?mbd.isSingleton():isSingleton(beanName));
    }

    /**
     * Check whether the specified bean would need to be eagerly initialized
     * in order to determine its type.
     * @param factoryBeanName a factory-bean reference that the bean definition
     *                        defines a factory method for
     * @return whether eager initialization is necessary
     */
    private boolean requiresEagerInitForType(@Nullable String factoryBeanName) {
        return (factoryBeanName != null && isFactoryBean(factoryBeanName) && !containsSingleton(factoryBeanName));
    }

    @Override
    public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type) throws BeansException {
        return getBeansOfType(type, true, true);
    }

    @Override
    @SuppressWarnings("unchecked")
    public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type, boolean includeNonSingletons,
                                             boolean allowEagerInit) throws BeansException {

        String[] beanNames = getBeanNamesForType(type, includeNonSingletons, allowEagerInit);
        Map<String, T> result = new LinkedHashMap<>(beanNames.length);
        for(String beanName: beanNames){
            try{
                Object beanInstance = getBean(beanName);
                if(!(beanInstance instanceof NullBean)){
                    result.put(beanName, (T)beanInstance);
                }
            }catch(BeanCreationException ex){
                Throwable rootCause = ex.getMostSpecificCause();
                if(rootCause instanceof BeanCurrentlyInCreationException){
                    BeanCreationException bce = (BeanCreationException)rootCause;
                    String exBeanName = bce.getBeanName();
                    if(exBeanName != null && isCurrentlyInCreation(exBeanName)){
                        if(logger.isTraceEnabled()){
                            logger.trace("Ignoring match to currently created bean '"
                                    + exBeanName
                                    + "': "
                                    + ex.getMessage());
                        }
                        onSuppressedException(ex);
                        // Ignore: indicates a circular reference when autowiring constructors.
                        // We want to find matches other than the currently created bean itself.
                        continue;
                    }
                }
                throw ex;
            }
        }
        return result;
    }

    @Override
    public String[] getBeanNamesForAnnotation(Class<? extends Annotation> annotationType) {
        List<String> result = new ArrayList<>();
        for(String beanName: this.beanDefinitionNames){
            BeanDefinition beanDefinition = getBeanDefinition(beanName);
            if(!beanDefinition.isAbstract() && findAnnotationOnBean(beanName, annotationType) != null){
                result.add(beanName);
            }
        }
        for(String beanName: this.manualSingletonNames){
            if(!result.contains(beanName) && findAnnotationOnBean(beanName, annotationType) != null){
                result.add(beanName);
            }
        }
        return StringUtils.toStringArray(result);
    }

    @Override
    public Map<String, Object> getBeansWithAnnotation(Class<? extends Annotation> annotationType) {
        String[] beanNames = getBeanNamesForAnnotation(annotationType);
        Map<String, Object> result = new LinkedHashMap<>(beanNames.length);
        for(String beanName: beanNames){
            Object beanInstance = getBean(beanName);
            if(!(beanInstance instanceof NullBean)){
                result.put(beanName, beanInstance);
            }
        }
        return result;
    }

    @Override
    @Nullable
    public <A extends Annotation> A findAnnotationOnBean(String beanName, Class<A> annotationType) throws NoSuchBeanDefinitionException {

        return findMergedAnnotationOnBean(beanName, annotationType).synthesize(MergedAnnotation::isPresent)
                                                                   .orElse(null);
    }

    private <A extends Annotation> MergedAnnotation<A> findMergedAnnotationOnBean(String beanName,
                                                                                  Class<A> annotationType) {

        Class<?> beanType = getType(beanName);
        if(beanType != null){
            MergedAnnotation<A> annotation = MergedAnnotations.from(beanType, SearchStrategy.TYPE_HIERARCHY)
                                                              .get(annotationType);
            if(annotation.isPresent()){
                return annotation;
            }
        }
        if(containsBeanDefinition(beanName)){
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            // Check raw bean class, e.g. in case of a proxy.
            if(bd.hasBeanClass()){
                Class<?> beanClass = bd.getBeanClass();
                if(beanClass != beanType){
                    MergedAnnotation<A> annotation = MergedAnnotations.from(beanClass, SearchStrategy.TYPE_HIERARCHY)
                                                                      .get(annotationType);
                    if(annotation.isPresent()){
                        return annotation;
                    }
                }
            }
            // Check annotations declared on factory method, if any.
            Method factoryMethod = bd.getResolvedFactoryMethod();
            if(factoryMethod != null){
                MergedAnnotation<A> annotation = MergedAnnotations.from(factoryMethod, SearchStrategy.TYPE_HIERARCHY)
                                                                  .get(annotationType);
                if(annotation.isPresent()){
                    return annotation;
                }
            }
        }
        return MergedAnnotation.missing();
    }

    //---------------------------------------------------------------------
    // Implementation of ConfigurableListableBeanFactory interface
    //---------------------------------------------------------------------

    @Override
    public void registerResolvableDependency(Class<?> dependencyType, @Nullable Object autowiredValue) {
        Assert.notNull(dependencyType, "Dependency type must not be null");
        if(autowiredValue != null){
            if(!(autowiredValue instanceof ObjectFactory || dependencyType.isInstance(autowiredValue))){
                throw new IllegalArgumentException("Value ["
                        + autowiredValue
                        + "] does not implement specified dependency type ["
                        + dependencyType.getName()
                        + "]");
            }
            this.resolvableDependencies.put(dependencyType, autowiredValue);
        }
    }

    @Override
    public boolean isAutowireCandidate(String beanName, DependencyDescriptor descriptor) throws NoSuchBeanDefinitionException {

        return isAutowireCandidate(beanName, descriptor, getAutowireCandidateResolver());
    }

    /**
     * Determine whether the specified bean definition qualifies as an autowire candidate,
     * to be injected into other beans which declare a dependency of matching type.
     * @param beanName   the name of the bean definition to check
     * @param descriptor the descriptor of the dependency to resolve
     * @param resolver   the AutowireCandidateResolver to use for the actual resolution algorithm
     * @return whether the bean should be considered as autowire candidate
     */
    protected boolean isAutowireCandidate(String beanName, DependencyDescriptor descriptor,
                                          AutowireCandidateResolver resolver) throws NoSuchBeanDefinitionException {

        String beanDefinitionName = BeanFactoryUtils.transformedBeanName(beanName);
        if(containsBeanDefinition(beanDefinitionName)){
            return isAutowireCandidate(beanName, getMergedLocalBeanDefinition(beanDefinitionName), descriptor,
                    resolver);
        }else if(containsSingleton(beanName)){
            return isAutowireCandidate(beanName, new RootBeanDefinition(getType(beanName)), descriptor, resolver);
        }

        BeanFactory parent = getParentBeanFactory();
        if(parent instanceof DefaultListableBeanFactory){
            // No bean definition found in this factory -> delegate to parent.
            return ((DefaultListableBeanFactory)parent).isAutowireCandidate(beanName, descriptor, resolver);
        }else if(parent instanceof ConfigurableListableBeanFactory){
            // If no DefaultListableBeanFactory, can't pass the resolver along.
            return ((ConfigurableListableBeanFactory)parent).isAutowireCandidate(beanName, descriptor);
        }else{
            return true;
        }
    }

    /**
     * Determine whether the specified bean definition qualifies as an autowire candidate,
     * to be injected into other beans which declare a dependency of matching type.
     * @param beanName   the name of the bean definition to check
     * @param mbd        the merged bean definition to check
     * @param descriptor the descriptor of the dependency to resolve
     * @param resolver   the AutowireCandidateResolver to use for the actual resolution algorithm
     * @return whether the bean should be considered as autowire candidate
     */
    protected boolean isAutowireCandidate(String beanName, RootBeanDefinition mbd, DependencyDescriptor descriptor,
                                          AutowireCandidateResolver resolver) {

        String beanDefinitionName = BeanFactoryUtils.transformedBeanName(beanName);
        resolveBeanClass(mbd, beanDefinitionName);
        if(mbd.isFactoryMethodUnique && mbd.factoryMethodToIntrospect == null){
            new ConstructorResolver(this).resolveFactoryMethodIfPossible(mbd);
        }
        return resolver.isAutowireCandidate(new BeanDefinitionHolder(mbd, beanName, getAliases(beanDefinitionName)),
                descriptor);
    }

    @Override
    public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
        BeanDefinition bd = this.beanDefinitionMap.get(beanName);
        if(bd == null){
            if(logger.isTraceEnabled()){
                logger.trace("No bean named '" + beanName + "' found in " + this);
            }
            throw new NoSuchBeanDefinitionException(beanName);
        }
        return bd;
    }

    @Override
    public Iterator<String> getBeanNamesIterator() {
        CompositeIterator<String> iterator = new CompositeIterator<>();
        iterator.add(this.beanDefinitionNames.iterator());
        iterator.add(this.manualSingletonNames.iterator());
        return iterator;
    }

    @Override
    public void clearMetadataCache() {
        super.clearMetadataCache();
        clearByTypeCache();
    }

    @Override
    public void freezeConfiguration() {
        this.configurationFrozen = true;
        this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
    }

    @Override
    public boolean isConfigurationFrozen() {
        return this.configurationFrozen;
    }

    /**
     * Considers all beans as eligible for metadata caching
     * if the factory's configuration has been marked as frozen.
     * @see #freezeConfiguration()
     */
    @Override
    protected boolean isBeanEligibleForMetadataCaching(String beanName) {
        return (this.configurationFrozen || super.isBeanEligibleForMetadataCaching(beanName));
    }

    @Override
    public void preInstantiateSingletons() throws BeansException {
        if(logger.isTraceEnabled()){
            logger.trace("Pre-instantiating singletons in " + this);
        }

        // Iterate over a copy to allow for init methods which in turn register new bean definitions.
        // While this may not be part of the regular factory bootstrap, it does otherwise work fine.
        List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

        // Trigger initialization of all non-lazy singleton beans...
        for(String beanName: beanNames){
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            if(!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()){
                if(isFactoryBean(beanName)){
                    Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
                    if(bean instanceof FactoryBean){
                        final FactoryBean<?> factory = (FactoryBean<?>)bean;
                        boolean isEagerInit;
                        if(System.getSecurityManager() != null && factory instanceof SmartFactoryBean){
                            isEagerInit =
                                    AccessController.doPrivileged((PrivilegedAction<Boolean>)((SmartFactoryBean<?>)factory)::isEagerInit, getAccessControlContext());
                        }else{
                            isEagerInit = (factory instanceof SmartFactoryBean
                                    && ((SmartFactoryBean<?>)factory).isEagerInit());
                        }
                        if(isEagerInit){
                            getBean(beanName);
                        }
                    }
                }else{
                    getBean(beanName);
                }
            }
        }

        // Trigger post-initialization callback for all applicable beans...
        // bean已完全处理完了
        // @EventListener标注的方法被DefaultEventListenerFactory包装成ApplicationListenerMethodAdapter
        //@EventListener中的classes就是事件对象
        //ApplicationListenerMethodApdapter注册到ApplicationContext中。
        //等待是事件源发布通知
        //通知后执行的逻辑就是标注@EventListener的方法的逻辑
        for(String beanName: beanNames){
            Object singletonInstance = getSingleton(beanName);
            if(singletonInstance instanceof SmartInitializingSingleton){
                final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton)singletonInstance;
                if(System.getSecurityManager() != null){
                    AccessController.doPrivileged((PrivilegedAction<Object>)() -> {
                        smartSingleton.afterSingletonsInstantiated();
                        return null;
                    }, getAccessControlContext());
                }else{
                    smartSingleton.afterSingletonsInstantiated();
                }
            }
        }
    }

    //---------------------------------------------------------------------
    // Implementation of BeanDefinitionRegistry interface
    //---------------------------------------------------------------------

    @Override
    public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException {

        Assert.hasText(beanName, "Bean name must not be empty");
        Assert.notNull(beanDefinition, "BeanDefinition must not be null");

        if(beanDefinition instanceof AbstractBeanDefinition){
            try{
                ((AbstractBeanDefinition)beanDefinition).validate();
            }catch(BeanDefinitionValidationException ex){
                throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation"
                        + " of bean definition failed", ex);
            }
        }

        BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
        //看看beanName是否已经存在容器里，存在则表明已经被注册过
        if(existingDefinition != null){
            if(!isAllowBeanDefinitionOverriding()){
                throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
            }else if(existingDefinition.getRole() < beanDefinition.getRole()){
                // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
                if(logger.isInfoEnabled()){
                    logger.info("Overriding user-defined bean definition for bean '"
                            + beanName
                            + "' with a framework-generated bean definition: replacing ["
                            + existingDefinition
                            + "] with ["
                            + beanDefinition
                            + "]");
                }
            }else if(!beanDefinition.equals(existingDefinition)){
                if(logger.isDebugEnabled()){
                    logger.debug("Overriding bean definition for bean '"
                            + beanName
                            + "' with a different definition: replacing ["
                            + existingDefinition
                            + "] with ["
                            + beanDefinition
                            + "]");
                }
            }else{
                if(logger.isTraceEnabled()){
                    logger.trace("Overriding bean definition for bean '"
                            + beanName
                            + "' with an equivalent definition: replacing ["
                            + existingDefinition
                            + "] with ["
                            + beanDefinition
                            + "]");
                }
            }
            this.beanDefinitionMap.put(beanName, beanDefinition);
        }else{
            if(hasBeanCreationStarted()){
                // Cannot modify startup-time collection elements anymore (for stable iteration)
                synchronized(this.beanDefinitionMap){
                    this.beanDefinitionMap.put(beanName, beanDefinition);
                    List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
                    updatedDefinitions.addAll(this.beanDefinitionNames);
                    updatedDefinitions.add(beanName);
                    this.beanDefinitionNames = updatedDefinitions;
                    removeManualSingletonName(beanName);
                }
            }else{
                // Still in startup registration phase
                this.beanDefinitionMap.put(beanName, beanDefinition);
                this.beanDefinitionNames.add(beanName);
                removeManualSingletonName(beanName);
            }
            this.frozenBeanDefinitionNames = null;
        }
        //检查是否有同名的BeanDefinition已经在IOC容器中注册
        if(existingDefinition != null || containsSingleton(beanName)){
            //尝试重置所有已经注册过的BeanDefinition的缓存，包括BeanDefinition
            //的父类以及合并的beanDefinition的缓存，所谓的合并BeanDefinition
            //指的的有parent属性的beandefinition，该BeanDefinition会把parent的
            //BeanDefinition属性合并在一块
            resetBeanDefinition(beanName);
        }
    }

    @Override
    public void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
        Assert.hasText(beanName, "'beanName' must not be empty");

        BeanDefinition bd = this.beanDefinitionMap.remove(beanName);
        if(bd == null){
            if(logger.isTraceEnabled()){
                logger.trace("No bean named '" + beanName + "' found in " + this);
            }
            throw new NoSuchBeanDefinitionException(beanName);
        }

        if(hasBeanCreationStarted()){
            // Cannot modify startup-time collection elements anymore (for stable iteration)
            synchronized(this.beanDefinitionMap){
                List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames);
                updatedDefinitions.remove(beanName);
                this.beanDefinitionNames = updatedDefinitions;
            }
        }else{
            // Still in startup registration phase
            this.beanDefinitionNames.remove(beanName);
        }
        this.frozenBeanDefinitionNames = null;

        resetBeanDefinition(beanName);
    }

    /**
     * Reset all bean definition caches for the given bean,
     * including the caches of beans that are derived from it.
     * <p>Called after an existing bean definition has been replaced or removed,
     * triggering {@link #clearMergedBeanDefinition}, {@link #destroySingleton}
     * and {@link MergedBeanDefinitionPostProcessor#resetBeanDefinition} on the
     * given bean and on all bean definitions that have the given bean as parent.
     * @param beanName the name of the bean to reset
     * @see #registerBeanDefinition
     * @see #removeBeanDefinition
     */
    protected void resetBeanDefinition(String beanName) {
        // Remove the merged bean definition for the given bean, if already created.
        clearMergedBeanDefinition(beanName);

        // Remove corresponding bean from singleton cache, if any. Shouldn't usually
        // be necessary, rather just meant for overriding a context's default beans
        // (e.g. the default StaticMessageSource in a StaticApplicationContext).
        destroySingleton(beanName);

        // Notify all post-processors that the specified bean definition has been reset.
        for(BeanPostProcessor processor: getBeanPostProcessors()){
            if(processor instanceof MergedBeanDefinitionPostProcessor){
                ((MergedBeanDefinitionPostProcessor)processor).resetBeanDefinition(beanName);
            }
        }

        // Reset all bean definitions that have the given bean as parent (recursively).
        for(String bdName: this.beanDefinitionNames){
            if(!beanName.equals(bdName)){
                BeanDefinition bd = this.beanDefinitionMap.get(bdName);
                // Ensure bd is non-null due to potential concurrent modification
                // of the beanDefinitionMap.
                if(bd != null && beanName.equals(bd.getParentName())){
                    resetBeanDefinition(bdName);
                }
            }
        }
    }

    /**
     * Only allows alias overriding if bean definition overriding is allowed.
     */
    @Override
    protected boolean allowAliasOverriding() {
        return isAllowBeanDefinitionOverriding();
    }

    @Override
    public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
        super.registerSingleton(beanName, singletonObject);
        updateManualSingletonNames(set -> set.add(beanName), set -> !this.beanDefinitionMap.containsKey(beanName));
        clearByTypeCache();
    }

    @Override
    public void destroySingletons() {
        super.destroySingletons();
        updateManualSingletonNames(Set::clear, set -> !set.isEmpty());
        clearByTypeCache();
    }

    @Override
    public void destroySingleton(String beanName) {
        super.destroySingleton(beanName);
        removeManualSingletonName(beanName);
        clearByTypeCache();
    }

    private void removeManualSingletonName(String beanName) {
        updateManualSingletonNames(set -> set.remove(beanName), set -> set.contains(beanName));
    }

    /**
     * Update the factory's internal set of manual singleton names.
     * @param action    the modification action
     * @param condition a precondition for the modification action
     *                  (if this condition does not apply, the action can be skipped)
     */
    private void updateManualSingletonNames(Consumer<Set<String>> action, Predicate<Set<String>> condition) {
        if(hasBeanCreationStarted()){
            // Cannot modify startup-time collection elements anymore (for stable iteration)
            synchronized(this.beanDefinitionMap){
                if(condition.test(this.manualSingletonNames)){
                    Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
                    action.accept(updatedSingletons);
                    this.manualSingletonNames = updatedSingletons;
                }
            }
        }else{
            // Still in startup registration phase
            if(condition.test(this.manualSingletonNames)){
                action.accept(this.manualSingletonNames);
            }
        }
    }

    /**
     * Remove any assumptions about by-type mappings.
     */
    private void clearByTypeCache() {
        this.allBeanNamesByType.clear();
        this.singletonBeanNamesByType.clear();
    }

    //---------------------------------------------------------------------
    // Dependency resolution functionality
    //---------------------------------------------------------------------

    @Override
    public <T> NamedBeanHolder<T> resolveNamedBean(Class<T> requiredType) throws BeansException {
        Assert.notNull(requiredType, "Required type must not be null");
        NamedBeanHolder<T> namedBean = resolveNamedBean(ResolvableType.forRawClass(requiredType), null, false);
        if(namedBean != null){
            return namedBean;
        }
        BeanFactory parent = getParentBeanFactory();
        if(parent instanceof AutowireCapableBeanFactory){
            return ((AutowireCapableBeanFactory)parent).resolveNamedBean(requiredType);
        }
        throw new NoSuchBeanDefinitionException(requiredType);
    }

    @SuppressWarnings("unchecked")
    @Nullable
    private <T> NamedBeanHolder<T> resolveNamedBean(ResolvableType requiredType, @Nullable Object[] args,
                                                    boolean nonUniqueAsNull) throws BeansException {

        Assert.notNull(requiredType, "Required type must not be null");
        String[] candidateNames = getBeanNamesForType(requiredType);

        if(candidateNames.length > 1){
            List<String> autowireCandidates = new ArrayList<>(candidateNames.length);
            for(String beanName: candidateNames){
                if(!containsBeanDefinition(beanName) || getBeanDefinition(beanName).isAutowireCandidate()){
                    autowireCandidates.add(beanName);
                }
            }
            if(!autowireCandidates.isEmpty()){
                candidateNames = StringUtils.toStringArray(autowireCandidates);
            }
        }

        if(candidateNames.length == 1){
            String beanName = candidateNames[0];
            return new NamedBeanHolder<>(beanName, (T)getBean(beanName, requiredType.toClass(), args));
        }else if(candidateNames.length > 1){
            Map<String, Object> candidates = new LinkedHashMap<>(candidateNames.length);
            for(String beanName: candidateNames){
                if(containsSingleton(beanName) && args == null){
                    Object beanInstance = getBean(beanName);
                    candidates.put(beanName, (beanInstance instanceof NullBean?null:beanInstance));
                }else{
                    candidates.put(beanName, getType(beanName));
                }
            }
            String candidateName = determinePrimaryCandidate(candidates, requiredType.toClass());
            if(candidateName == null){
                candidateName = determineHighestPriorityCandidate(candidates, requiredType.toClass());
            }
            if(candidateName != null){
                Object beanInstance = candidates.get(candidateName);
                if(beanInstance == null || beanInstance instanceof Class){
                    beanInstance = getBean(candidateName, requiredType.toClass(), args);
                }
                return new NamedBeanHolder<>(candidateName, (T)beanInstance);
            }
            if(!nonUniqueAsNull){
                throw new NoUniqueBeanDefinitionException(requiredType, candidates.keySet());
            }
        }

        return null;
    }

    @Override
    @Nullable
    public Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName,
                                    @Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {

        descriptor.initParameterNameDiscovery(getParameterNameDiscoverer());
        if(Optional.class == descriptor.getDependencyType()){
            return createOptionalDependency(descriptor, requestingBeanName);
        }else if(ObjectFactory.class == descriptor.getDependencyType()
                || ObjectProvider.class == descriptor.getDependencyType()){
            return new DependencyObjectProvider(descriptor, requestingBeanName);
        }else if(javaxInjectProviderClass == descriptor.getDependencyType()){
            return new Jsr330Factory().createDependencyProvider(descriptor, requestingBeanName);
        }else{
            Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(descriptor,
                    requestingBeanName);
            if(result == null){
                // 解析依赖
                result = doResolveDependency(descriptor, requestingBeanName, autowiredBeanNames, typeConverter);
            }
            return result;
        }
    }

    @Nullable
    public Object doResolveDependency(DependencyDescriptor descriptor, @Nullable String beanName,
                                      @Nullable Set<String> autowiredBeanNames,
                                      @Nullable TypeConverter typeConverter) throws BeansException {

        InjectionPoint previousInjectionPoint = ConstructorResolver.setCurrentInjectionPoint(descriptor);
        try{
            // 该方法最终调用了 beanFactory.getBean(String, Class)，从容器中获取依赖
            Object shortcut = descriptor.resolveShortcut(this);
            // 如果容器缓存中存在所需依赖，这里进行短路路操作，提前结束依赖解析逻辑
            if(shortcut != null){
                return shortcut;
            }

            Class<?> type = descriptor.getDependencyType();
            // 处理 @value 注解
            Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
            if(value != null){
                if(value instanceof String){
                    String strVal = resolveEmbeddedValue((String)value);
                    BeanDefinition bd = (beanName != null
                                                 && containsBean(beanName)?getMergedBeanDefinition(beanName):null);
                    value = evaluateBeanDefinitionString(strVal, bd);
                }
                TypeConverter converter = (typeConverter != null?typeConverter:getTypeConverter());
                try{
                    return converter.convertIfNecessary(value, type, descriptor.getTypeDescriptor());
                }catch(UnsupportedOperationException ex){
                    // A custom TypeConverter which does not support TypeDescriptor resolution...
                    return (descriptor.getField()
                                    != null?converter.convertIfNecessary(value, type, descriptor.getField()):
                            converter.convertIfNecessary(value, type, descriptor
                            .getMethodParameter()));
                }
            }
            //如果标识@Autowired注解的成员变量是复合类型，如Array,Collection,Map,
            // 从这个方法获取@Autowired里的值
            Object multipleBeans = resolveMultipleBeans(descriptor, beanName, autowiredBeanNames, typeConverter);
            if(multipleBeans != null){
                return multipleBeans;
            }
            //	如果标识@Autowired注解的属性是非复合类型，
            // 从这个方法获取@Autowired里的值
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
            if(matchingBeans.isEmpty()){
                // 没有找到，检验 @autowire  的 require 是否为 true
                if(isRequired(descriptor)){
                    // 如果 @autowire 的 require 属性为 true ，但是没有找到相应的匹配项，则抛出异常
                    raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
                }
                return null;
            }

            String autowiredBeanName;
            Object instanceCandidate;

            if(matchingBeans.size() > 1){
                //如果被@Autowired标记的有两个以上同样的类型，
                // 就需要依据@Primary以及@Priority注解标签选择了
                autowiredBeanName = determineAutowireCandidate(matchingBeans, descriptor);
                if(autowiredBeanName == null){
                    if(isRequired(descriptor) || !indicatesMultipleBeans(type)){
                        //无法选出唯一的，则直接报错
                        return descriptor.resolveNotUnique(descriptor.getResolvableType(), matchingBeans);
                    }else{
                        // In case of an optional Collection/Map, silently ignore a non-unique case:
                        // possibly it was meant to be an empty collection of multiple regular beans
                        // (before 4.3 in particular when we didn't even look for collection beans).
                        return null;
                    }
                }
                instanceCandidate = matchingBeans.get(autowiredBeanName);
            }else{
                // We have exactly one match.
                Map.Entry<String, Object> entry = matchingBeans.entrySet().iterator().next();
                autowiredBeanName = entry.getKey();
                instanceCandidate = entry.getValue();
            }

            if(autowiredBeanNames != null){
                autowiredBeanNames.add(autowiredBeanName);
            }
            if(instanceCandidate instanceof Class){
                instanceCandidate = descriptor.resolveCandidate(autowiredBeanName, type, this);
            }
            Object result = instanceCandidate;
            if(result instanceof NullBean){
                if(isRequired(descriptor)){
                    raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
                }
                result = null;
            }
            if(!ClassUtils.isAssignableValue(type, result)){
                throw new BeanNotOfRequiredTypeException(autowiredBeanName, type, instanceCandidate.getClass());
            }
            return result;
        }finally{
            ConstructorResolver.setCurrentInjectionPoint(previousInjectionPoint);
        }
    }

    @Nullable
    private Object resolveMultipleBeans(DependencyDescriptor descriptor, @Nullable String beanName,
                                        @Nullable Set<String> autowiredBeanNames,
                                        @Nullable TypeConverter typeConverter) {

        final Class<?> type = descriptor.getDependencyType();
        //首先是stream类型的处理
        if(descriptor instanceof StreamDependencyDescriptor){
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
            if(autowiredBeanNames != null){
                autowiredBeanNames.addAll(matchingBeans.keySet());
            }
            Stream<Object> stream = matchingBeans.keySet()
                                                 .stream()
                                                 .map(name -> descriptor.resolveCandidate(name, type, this))
                                                 .filter(bean -> !(bean instanceof NullBean));
            if(((StreamDependencyDescriptor)descriptor).isOrdered()){
                stream = stream.sorted(adaptOrderComparator(matchingBeans));
            }
            return stream;
        }
        // 判断要注入的是不是一个数组，可见除了集合注入外，也可以以数组的形式注入bean
        else if(type.isArray()){
            Class<?> componentType = type.getComponentType();
            ResolvableType resolvableType = descriptor.getResolvableType();
            Class<?> resolvedArrayType = resolvableType.resolve(type);
            if(resolvedArrayType != type){
                componentType = resolvableType.getComponentType().resolve();
            }
            if(componentType == null){
                return null;
            }
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, componentType,
                    new MultiElementDescriptor(descriptor));
            if(matchingBeans.isEmpty()){
                return null;
            }
            if(autowiredBeanNames != null){
                autowiredBeanNames.addAll(matchingBeans.keySet());
            }
            TypeConverter converter = (typeConverter != null?typeConverter:getTypeConverter());
            Object result = converter.convertIfNecessary(matchingBeans.values(), resolvedArrayType);
            if(result instanceof Object[]){
                Comparator<Object> comparator = adaptDependencyComparator(matchingBeans);
                if(comparator != null){
                    Arrays.sort((Object[])result, comparator);
                }
            }
            return result;
        }
        //判断注入的是不是集合的接口类（List、Set等）
        else if(Collection.class.isAssignableFrom(type) && type.isInterface()){
            Class<?> elementType = descriptor.getResolvableType().asCollection().resolveGeneric();
            if(elementType == null){
                return null;
            }
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, elementType,
                    new MultiElementDescriptor(descriptor));
            if(matchingBeans.isEmpty()){
                return null;
            }
            if(autowiredBeanNames != null){
                autowiredBeanNames.addAll(matchingBeans.keySet());
            }
            TypeConverter converter = (typeConverter != null?typeConverter:getTypeConverter());
            Object result = converter.convertIfNecessary(matchingBeans.values(), type);
            if(result instanceof List){
                Comparator<Object> comparator = adaptDependencyComparator(matchingBeans);
                if(comparator != null){
                    ((List<?>)result).sort(comparator);
                }
            }
            return result;
        }
        // 判断要注入的是不是map类
        else if(Map.class == type){
            ResolvableType mapType = descriptor.getResolvableType().asMap();
            Class<?> keyType = mapType.resolveGeneric(0);
            if(String.class != keyType){
                return null;
            }
            Class<?> valueType = mapType.resolveGeneric(1);
            if(valueType == null){
                return null;
            }
            Map<String, Object> matchingBeans = findAutowireCandidates(beanName, valueType,
                    new MultiElementDescriptor(descriptor));
            if(matchingBeans.isEmpty()){
                return null;
            }
            if(autowiredBeanNames != null){
                autowiredBeanNames.addAll(matchingBeans.keySet());
            }
            return matchingBeans;
        }else{
            return null;
        }
    }

    private boolean isRequired(DependencyDescriptor descriptor) {
        return getAutowireCandidateResolver().isRequired(descriptor);
    }

    private boolean indicatesMultipleBeans(Class<?> type) {
        return (type.isArray() || (type.isInterface() && (Collection.class.isAssignableFrom(type)
                || Map.class.isAssignableFrom(type))));
    }

    @Nullable
    private Comparator<Object> adaptDependencyComparator(Map<String, ?> matchingBeans) {
        Comparator<Object> comparator = getDependencyComparator();
        if(comparator instanceof OrderComparator){
            return ((OrderComparator)comparator).withSourceProvider(createFactoryAwareOrderSourceProvider(matchingBeans));
        }else{
            return comparator;
        }
    }

    private Comparator<Object> adaptOrderComparator(Map<String, ?> matchingBeans) {
        Comparator<Object> dependencyComparator = getDependencyComparator();
        OrderComparator comparator = (dependencyComparator instanceof OrderComparator?
                                      (OrderComparator)dependencyComparator:OrderComparator.INSTANCE);
        return comparator.withSourceProvider(createFactoryAwareOrderSourceProvider(matchingBeans));
    }

    private OrderComparator.OrderSourceProvider createFactoryAwareOrderSourceProvider(Map<String, ?> beans) {
        IdentityHashMap<Object, String> instancesToBeanNames = new IdentityHashMap<>();
        beans.forEach((beanName, instance) -> instancesToBeanNames.put(instance, beanName));
        return new FactoryAwareOrderSourceProvider(instancesToBeanNames);
    }

    /**
     * Find bean instances that match the required type.
     * Called during autowiring for the specified bean.
     * @param beanName     the name of the bean that is about to be wired
     * @param requiredType the actual type of bean to look for
     *                     (may be an array component type or collection element type)
     * @param descriptor   the descriptor of the dependency to resolve
     * @return a Map of candidate names and candidate instances that match
     *         the required type (never {@code null})
     * @throws BeansException in case of errors
     * @see #autowireByType
     * @see #autowireConstructor
     */
    protected Map<String, Object> findAutowireCandidates(@Nullable String beanName, Class<?> requiredType,
                                                         DependencyDescriptor descriptor) {
        //查找出所有符合类型的 beanName
        String[] candidateNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this, requiredType, true,
                descriptor
                .isEager());
        Map<String, Object> result = new LinkedHashMap<>(candidateNames.length);
        //resolvableDependencies 记录了属性类型--值 的映射
        for(Map.Entry<Class<?>, Object> classObjectEntry: this.resolvableDependencies.entrySet()){
            Class<?> autowiringType = classObjectEntry.getKey();
            if(autowiringType.isAssignableFrom(requiredType)){
                Object autowiringValue = classObjectEntry.getValue();
                //key值是我们需要的类型
                // 但value可能是ObjectFactory，如果是就得调用它的 getObject() 来获取真正的bean.
                autowiringValue = AutowireUtils.resolveAutowiringValue(autowiringValue, requiredType);
                if(requiredType.isInstance(autowiringValue)){
                    //如果类型匹配，则塞入result
                    result.put(ObjectUtils.identityToString(autowiringValue), autowiringValue);
                    break;
                }
            }
        }
        //遍历候选数组
        for(String candidate: candidateNames){
            //候选Bean不是自引用（即要注入的类不能是类本身，会触发无限递归注入）
            if(!isSelfReference(beanName, candidate) && isAutowireCandidate(candidate, descriptor)){
                addCandidateEntry(result, candidate, descriptor, requiredType);
            }
        }
        if(result.isEmpty()){
            boolean multiple = indicatesMultipleBeans(requiredType);
            // Consider fallback matches if the first pass failed to find anything...
            DependencyDescriptor fallbackDescriptor = descriptor.forFallbackMatch();
            for(String candidate: candidateNames){
                if(!isSelfReference(beanName, candidate)
                        && isAutowireCandidate(candidate, fallbackDescriptor)
                        && (!multiple || getAutowireCandidateResolver().hasQualifier(descriptor))){
                    addCandidateEntry(result, candidate, descriptor, requiredType);
                }
            }
            if(result.isEmpty() && !multiple){
                // Consider self references as a final pass...
                // but in the case of a dependency collection, not the very same bean itself.
                for(String candidate: candidateNames){
                    if(isSelfReference(beanName, candidate) && (!(descriptor instanceof MultiElementDescriptor)
                            || !beanName.equals(candidate)) && isAutowireCandidate(candidate, fallbackDescriptor)){
                        addCandidateEntry(result, candidate, descriptor, requiredType);
                    }
                }
            }
        }
        return result;
    }

    /**
     * Add an entry to the candidate map: a bean instance if available or just the resolved
     * type, preventing early bean initialization ahead of primary candidate selection.
     */
    private void addCandidateEntry(Map<String, Object> candidates, String candidateName,
                                   DependencyDescriptor descriptor, Class<?> requiredType) {
        //若@Autowired标识的是容器类型的属性，生成的依赖描述类型是MultiElementDescriptor ，
        //这种情况下，由于所有的候选对象均是合格的，会当场实例化他们。
        // 而如果属性的类型非容器，那么可能是多个候选对象中挑一个，
        //此时实例化他们所有就不合适了，最终会把合格的那个实例化，如果没有合格的则不实例化，
        if(descriptor instanceof MultiElementDescriptor){
            Object beanInstance = descriptor.resolveCandidate(candidateName, requiredType, this);
            if(!(beanInstance instanceof NullBean)){
                candidates.put(candidateName, beanInstance);
            }
        }else if(containsSingleton(candidateName) || (descriptor instanceof StreamDependencyDescriptor
                && ((StreamDependencyDescriptor)descriptor).isOrdered())){
            Object beanInstance = descriptor.resolveCandidate(candidateName, requiredType, this);
            candidates.put(candidateName, (beanInstance instanceof NullBean?null:beanInstance));
        }else{
            candidates.put(candidateName, getType(candidateName));
        }
    }

    /**
     * Determine the autowire candidate in the given set of beans.
     * <p>Looks for {@code @Primary} and {@code @Priority} (in that order).
     * @param candidates a Map of candidate names and candidate instances
     *                   that match the required type, as returned by {@link #findAutowireCandidates}
     * @param descriptor the target dependency to match against
     * @return the name of the autowire candidate, or {@code null} if none found
     */
    @Nullable
    protected String determineAutowireCandidate(Map<String, Object> candidates, DependencyDescriptor descriptor) {
        Class<?> requiredType = descriptor.getDependencyType();
        //根据@Primary注解标签来选择最优解
        String primaryCandidate = determinePrimaryCandidate(candidates, requiredType);
        if(primaryCandidate != null){
            return primaryCandidate;
        }
        //根据@Order,@PriorityOrder，及实现Order接口的序号来选择最优解，选序号最小的
        String priorityCandidate = determineHighestPriorityCandidate(candidates, requiredType);
        if(priorityCandidate != null){
            return priorityCandidate;
        }
        // Fallback
        for(Map.Entry<String, Object> entry: candidates.entrySet()){
            String candidateName = entry.getKey();
            Object beanInstance = entry.getValue();
            //如果通过以上两步都不能选出最优解，则:
            //如果这个类型已经由Spring注册过依赖关系对，则直接使用注册的对象，
            //候选者集合是LinkedHashMap,有序Map集合，容器注册的依赖对象位于LinkedHashMap的起始位置
            //如果没有注册过此类型的依赖关系，则根据属性的名称来匹配，
            //如果属性名称和某个候选者的Bean名称或别名一致，那么直接将此Bean作为最优解
            if((beanInstance != null && this.resolvableDependencies.containsValue(beanInstance))
                    || matchesBeanName(candidateName, descriptor.getDependencyName())){
                return candidateName;
            }
        }
        return null;
    }

    /**
     * Determine the primary candidate in the given set of beans.
     * @param candidates   a Map of candidate names and candidate instances
     *                     (or candidate classes if not created yet) that match the required type
     * @param requiredType the target dependency type to match against
     * @return the name of the primary candidate, or {@code null} if none found
     * @see #isPrimary(String, Object)
     */
    @Nullable
    protected String determinePrimaryCandidate(Map<String, Object> candidates, Class<?> requiredType) {
        String primaryBeanName = null;
        for(Map.Entry<String, Object> entry: candidates.entrySet()){
            String candidateBeanName = entry.getKey();
            Object beanInstance = entry.getValue();
            //候选者可以是当前容器或者父容器内的标识了@Primary的Bean
            if(isPrimary(candidateBeanName, beanInstance)){
                if(primaryBeanName != null){
                    boolean candidateLocal = containsBeanDefinition(candidateBeanName);
                    boolean primaryLocal = containsBeanDefinition(primaryBeanName);
                    //确保同一个容器中同一个类型的多个Bean最多只有一个Bean标识了@Primary
                    if(candidateLocal && primaryLocal){
                        throw new NoUniqueBeanDefinitionException(requiredType, candidates.size(),
                                "more than one 'primary' bean found among candidates: "
                                        + candidates.keySet());
                    }
                    //如果上一个@Primary的Bean是父容器的，则用当前容器的候选者覆盖之前的@Primary的Bean
                    else if(candidateLocal){
                        primaryBeanName = candidateBeanName;
                    }
                }else{
                    primaryBeanName = candidateBeanName;
                }
            }
        }
        return primaryBeanName;
    }

    /**
     * Determine the candidate with the highest priority in the given set of beans.
     * <p>Based on {@code @javax.annotation.Priority}. As defined by the related
     * {@link org.springframework.core.Ordered} interface, the lowest value has
     * the highest priority.
     * @param candidates   a Map of candidate names and candidate instances
     *                     (or candidate classes if not created yet) that match the required type
     * @param requiredType the target dependency type to match against
     * @return the name of the candidate with the highest priority,
     *         or {@code null} if none found
     * @see #getPriority(Object)
     */
    @Nullable
    protected String determineHighestPriorityCandidate(Map<String, Object> candidates, Class<?> requiredType) {
        String highestPriorityBeanName = null;
        Integer highestPriority = null;
        for(Map.Entry<String, Object> entry: candidates.entrySet()){
            String candidateBeanName = entry.getKey();
            Object beanInstance = entry.getValue();
            if(beanInstance != null){
                Integer candidatePriority = getPriority(beanInstance);
                if(candidatePriority != null){
                    //不能同时存在两个最高优先级的序号
                    if(highestPriorityBeanName != null){
                        if(candidatePriority.equals(highestPriority)){
                            throw new NoUniqueBeanDefinitionException(requiredType, candidates.size(),
                                    "Multiple beans found with the same priority ('"
                                            + highestPriority
                                            + "') among candidates: "
                                            + candidates.keySet());
                        }
                        //使用优先级序号最小的Bean实例作为最优解
                        else if(candidatePriority < highestPriority){
                            highestPriorityBeanName = candidateBeanName;
                            highestPriority = candidatePriority;
                        }
                    }else{
                        highestPriorityBeanName = candidateBeanName;
                        highestPriority = candidatePriority;
                    }
                }
            }
        }
        return highestPriorityBeanName;
    }

    /**
     * Return whether the bean definition for the given bean name has been
     * marked as a primary bean.
     * @param beanName     the name of the bean
     * @param beanInstance the corresponding bean instance (can be null)
     * @return whether the given bean qualifies as primary
     */
    protected boolean isPrimary(String beanName, Object beanInstance) {
        String transformedBeanName = transformedBeanName(beanName);
        if(containsBeanDefinition(transformedBeanName)){
            return getMergedLocalBeanDefinition(transformedBeanName).isPrimary();
        }
        BeanFactory parent = getParentBeanFactory();
        return (parent instanceof DefaultListableBeanFactory
                && ((DefaultListableBeanFactory)parent).isPrimary(transformedBeanName, beanInstance));
    }

    /**
     * Return the priority assigned for the given bean instance by
     * the {@code javax.annotation.Priority} annotation.
     * <p>The default implementation delegates to the specified
     * {@link #setDependencyComparator dependency comparator}, checking its
     * {@link OrderComparator#getPriority method} if it is an extension of
     * Spring's common {@link OrderComparator} - typically, an
     * {@link org.springframework.core.annotation.AnnotationAwareOrderComparator}.
     * If no such comparator is present, this implementation returns {@code null}.
     * @param beanInstance the bean instance to check (can be {@code null})
     * @return the priority assigned to that bean or {@code null} if none is set
     */
    @Nullable
    protected Integer getPriority(Object beanInstance) {
        Comparator<Object> comparator = getDependencyComparator();
        if(comparator instanceof OrderComparator){
            return ((OrderComparator)comparator).getPriority(beanInstance);
        }
        return null;
    }

    /**
     * Determine whether the given candidate name matches the bean name or the aliases
     * stored in this bean definition.
     */
    protected boolean matchesBeanName(String beanName, @Nullable String candidateName) {
        return (candidateName != null && (candidateName.equals(beanName)
                || ObjectUtils.containsElement(getAliases(beanName), candidateName)));
    }

    /**
     * Determine whether the given beanName/candidateName pair indicates a self reference,
     * i.e. whether the candidate points back to the original bean or to a factory method
     * on the original bean.
     */
    private boolean isSelfReference(@Nullable String beanName, @Nullable String candidateName) {
        return (beanName != null && candidateName != null && (beanName.equals(candidateName)
                || (containsBeanDefinition(candidateName) && beanName.equals(getMergedLocalBeanDefinition(candidateName)
                .getFactoryBeanName()))));
    }

    /**
     * Raise a NoSuchBeanDefinitionException or BeanNotOfRequiredTypeException
     * for an unresolvable dependency.
     */
    private void raiseNoMatchingBeanFound(Class<?> type, ResolvableType resolvableType,
                                          DependencyDescriptor descriptor) throws BeansException {

        checkBeanNotOfRequiredType(type, descriptor);

        throw new NoSuchBeanDefinitionException(resolvableType,
                "expected at least 1 bean which qualifies as autowire candidate. "
                        + "Dependency annotations: "
                        + ObjectUtils.nullSafeToString(descriptor.getAnnotations()));
    }

    /**
     * Raise a BeanNotOfRequiredTypeException for an unresolvable dependency, if applicable,
     * i.e. if the target type of the bean would match but an exposed proxy doesn't.
     */
    private void checkBeanNotOfRequiredType(Class<?> type, DependencyDescriptor descriptor) {
        for(String beanName: this.beanDefinitionNames){
            RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
            Class<?> targetType = mbd.getTargetType();
            if(targetType != null
                    && type.isAssignableFrom(targetType)
                    && isAutowireCandidate(beanName, mbd, descriptor, getAutowireCandidateResolver())){
                // Probably a proxy interfering with target type match -> throw meaningful exception.
                Object beanInstance = getSingleton(beanName, false);
                Class<?> beanType = (beanInstance != null
                                             && beanInstance.getClass()
                        != NullBean.class?beanInstance.getClass():predictBeanType(beanName, mbd));
                if(beanType != null && !type.isAssignableFrom(beanType)){
                    throw new BeanNotOfRequiredTypeException(beanName, type, beanType);
                }
            }
        }

        BeanFactory parent = getParentBeanFactory();
        if(parent instanceof DefaultListableBeanFactory){
            ((DefaultListableBeanFactory)parent).checkBeanNotOfRequiredType(type, descriptor);
        }
    }

    /**
     * Create an {@link Optional} wrapper for the specified dependency.
     */
    private Optional<?> createOptionalDependency(DependencyDescriptor descriptor, @Nullable String beanName,
                                                 final Object... args) {

        DependencyDescriptor descriptorToUse = new NestedDependencyDescriptor(descriptor) {
            @Override
            public boolean isRequired() {
                return false;
            }

            @Override
            public Object resolveCandidate(String beanName, Class<?> requiredType, BeanFactory beanFactory) {
                return (!ObjectUtils.isEmpty(args)?beanFactory.getBean(beanName, args):
                        super.resolveCandidate(beanName, requiredType, beanFactory));
            }
        };
        Object result = doResolveDependency(descriptorToUse, beanName, null, null);
        return (result instanceof Optional?(Optional<?>)result:Optional.ofNullable(result));
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder(ObjectUtils.identityToString(this));
        sb.append(": defining beans [");
        sb.append(StringUtils.collectionToCommaDelimitedString(this.beanDefinitionNames));
        sb.append("]; ");
        BeanFactory parent = getParentBeanFactory();
        if(parent == null){
            sb.append("root of factory hierarchy");
        }else{
            sb.append("parent: ").append(ObjectUtils.identityToString(parent));
        }
        return sb.toString();
    }

    //---------------------------------------------------------------------
    // Serialization support
    //---------------------------------------------------------------------

    private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
        throw new NotSerializableException("DefaultListableBeanFactory itself is not deserializable - "
                + "just a SerializedBeanFactoryReference is");
    }

    protected Object writeReplace() throws ObjectStreamException {
        if(this.serializationId != null){
            return new SerializedBeanFactoryReference(this.serializationId);
        }else{
            throw new NotSerializableException("DefaultListableBeanFactory has no serialization id");
        }
    }

    /**
     * Minimal id reference to the factory.
     * Resolved to the actual factory instance on deserialization.
     */
    private static class SerializedBeanFactoryReference implements Serializable {

        private final String id;

        public SerializedBeanFactoryReference(String id) {
            this.id = id;
        }

        private Object readResolve() {
            Reference<?> ref = serializableFactories.get(this.id);
            if(ref != null){
                Object result = ref.get();
                if(result != null){
                    return result;
                }
            }
            // Lenient fallback: dummy factory in case of original factory not found...
            DefaultListableBeanFactory dummyFactory = new DefaultListableBeanFactory();
            dummyFactory.serializationId = this.id;
            return dummyFactory;
        }

    }

    /**
     * A dependency descriptor marker for nested elements.
     */
    private static class NestedDependencyDescriptor extends DependencyDescriptor {

        public NestedDependencyDescriptor(DependencyDescriptor original) {
            super(original);
            increaseNestingLevel();
        }

    }

    /**
     * A dependency descriptor for a multi-element declaration with nested elements.
     */
    private static class MultiElementDescriptor extends NestedDependencyDescriptor {

        public MultiElementDescriptor(DependencyDescriptor original) {
            super(original);
        }

    }

    /**
     * A dependency descriptor marker for stream access to multiple elements.
     */
    private static class StreamDependencyDescriptor extends DependencyDescriptor {

        private final boolean ordered;

        public StreamDependencyDescriptor(DependencyDescriptor original, boolean ordered) {
            super(original);
            this.ordered = ordered;
        }

        public boolean isOrdered() {
            return this.ordered;
        }

    }

    private interface BeanObjectProvider<T> extends ObjectProvider<T>, Serializable {}

    /**
     * Serializable ObjectFactory/ObjectProvider for lazy resolution of a dependency.
     */
    private class DependencyObjectProvider implements BeanObjectProvider<Object> {

        private final DependencyDescriptor descriptor;

        private final boolean optional;

        @Nullable
        private final String beanName;

        public DependencyObjectProvider(DependencyDescriptor descriptor, @Nullable String beanName) {
            this.descriptor = new NestedDependencyDescriptor(descriptor);
            this.optional = (this.descriptor.getDependencyType() == Optional.class);
            this.beanName = beanName;
        }

        @Override
        public Object getObject() throws BeansException {
            if(this.optional){
                return createOptionalDependency(this.descriptor, this.beanName);
            }else{
                Object result = doResolveDependency(this.descriptor, this.beanName, null, null);
                if(result == null){
                    throw new NoSuchBeanDefinitionException(this.descriptor.getResolvableType());
                }
                return result;
            }
        }

        @Override
        public Object getObject(final Object... args) throws BeansException {
            if(this.optional){
                return createOptionalDependency(this.descriptor, this.beanName, args);
            }else{
                DependencyDescriptor descriptorToUse = new DependencyDescriptor(this.descriptor) {
                    @Override
                    public Object resolveCandidate(String beanName, Class<?> requiredType, BeanFactory beanFactory) {
                        return beanFactory.getBean(beanName, args);
                    }
                };
                Object result = doResolveDependency(descriptorToUse, this.beanName, null, null);
                if(result == null){
                    throw new NoSuchBeanDefinitionException(this.descriptor.getResolvableType());
                }
                return result;
            }
        }

        @Override
        @Nullable
        public Object getIfAvailable() throws BeansException {
            if(this.optional){
                return createOptionalDependency(this.descriptor, this.beanName);
            }else{
                DependencyDescriptor descriptorToUse = new DependencyDescriptor(this.descriptor) {
                    @Override
                    public boolean isRequired() {
                        return false;
                    }
                };
                return doResolveDependency(descriptorToUse, this.beanName, null, null);
            }
        }

        @Override
        @Nullable
        public Object getIfUnique() throws BeansException {
            DependencyDescriptor descriptorToUse = new DependencyDescriptor(this.descriptor) {
                @Override
                public boolean isRequired() {
                    return false;
                }

                @Override
                @Nullable
                public Object resolveNotUnique(ResolvableType type, Map<String, Object> matchingBeans) {
                    return null;
                }
            };
            if(this.optional){
                return createOptionalDependency(descriptorToUse, this.beanName);
            }else{
                return doResolveDependency(descriptorToUse, this.beanName, null, null);
            }
        }

        @Nullable
        protected Object getValue() throws BeansException {
            if(this.optional){
                return createOptionalDependency(this.descriptor, this.beanName);
            }else{
                return doResolveDependency(this.descriptor, this.beanName, null, null);
            }
        }

        @Override
        public Stream<Object> stream() {
            return resolveStream(false);
        }

        @Override
        public Stream<Object> orderedStream() {
            return resolveStream(true);
        }

        @SuppressWarnings("unchecked")
        private Stream<Object> resolveStream(boolean ordered) {
            DependencyDescriptor descriptorToUse = new StreamDependencyDescriptor(this.descriptor, ordered);
            Object result = doResolveDependency(descriptorToUse, this.beanName, null, null);
            return (result instanceof Stream?(Stream<Object>)result:Stream.of(result));
        }

    }

    /**
     * Separate inner class for avoiding a hard dependency on the {@code javax.inject} API.
     * Actual {@code javax.inject.Provider} implementation is nested here in order to make it
     * invisible for Graal's introspection of DefaultListableBeanFactory's nested classes.
     */
    private class Jsr330Factory implements Serializable {

        public Object createDependencyProvider(DependencyDescriptor descriptor, @Nullable String beanName) {
            return new Jsr330Provider(descriptor, beanName);
        }

        private class Jsr330Provider extends DependencyObjectProvider implements Provider<Object> {

            public Jsr330Provider(DependencyDescriptor descriptor, @Nullable String beanName) {
                super(descriptor, beanName);
            }

            @Override
            @Nullable
            public Object get() throws BeansException {
                return getValue();
            }

        }

    }

    /**
     * An {@link org.springframework.core.OrderComparator.OrderSourceProvider} implementation
     * that is aware of the bean metadata of the instances to sort.
     * <p>Lookup for the method factory of an instance to sort, if any, and let the
     * comparator retrieve the {@link org.springframework.core.annotation.Order}
     * value defined on it. This essentially allows for the following construct:
     */
    private class FactoryAwareOrderSourceProvider implements OrderComparator.OrderSourceProvider {

        private final Map<Object, String> instancesToBeanNames;

        public FactoryAwareOrderSourceProvider(Map<Object, String> instancesToBeanNames) {
            this.instancesToBeanNames = instancesToBeanNames;
        }

        @Override
        @Nullable
        public Object getOrderSource(Object obj) {
            String beanName = this.instancesToBeanNames.get(obj);
            if(beanName == null || !containsBeanDefinition(beanName)){
                return null;
            }
            RootBeanDefinition beanDefinition = getMergedLocalBeanDefinition(beanName);
            List<Object> sources = new ArrayList<>(2);
            Method factoryMethod = beanDefinition.getResolvedFactoryMethod();
            if(factoryMethod != null){
                sources.add(factoryMethod);
            }
            Class<?> targetType = beanDefinition.getTargetType();
            if(targetType != null && targetType != obj.getClass()){
                sources.add(targetType);
            }
            return sources.toArray();
        }

    }

}
